The Zero-Backlash CNC Rotary TableRollerDrive CNCTM

The answer for a CNC rotary axis

Pure Motion By Zero-Backlash Technology

No Clamp Operation

Perpetual Precision

RollerDrive motion

Actual motion with distortion pronedrives

Dis

plac

emen

t D

ispl

acem

ent

Time

Time

CNCRollerDrive TM

The RollerDrive CNC, a CNC rotary table, is designed to fulfill the demands of the latest machine tools for increased speed and precision. Inside, the RollerDrive CNC uses a RollerDrive, our zero-backlash reducer which transmits motion without distortions while staying robust against external forces unlike existing gears and torque motors. The high precision and rigidity achieved by the zero-backlash technology gives the RollerDrive CNC a rotational accuracy of less than ±10 arc sec. and repeatability of less than ±4 arc sec., and remains robust while doing heavy cutting work on hard metals.

The RollerDrive CNC does not require a clamp operation due to its mechanically rigid zero-backlash structure. This eliminates clamp and unclamp time and requires no energy like conventional hydraulic/air systems. Combined, the distortion-free performance and no-clamp design delivers ultra fast positioning that leads to higher productivity. For instance, a typical 90-degree rotation can be done within 0.4 seconds.

The unique mechanism of the RollerDrive makes the RollerDrive CNC capable of withstanding years of operation without internal part wear or loss of precision. Regular calibration or readjustment work is unnecessary for the RollerDrive CNC.

OverviewRollerDrive CNCTM

Mechanism

Output angle

0 90 180 270 360-0.02

-0.01

0.01

0

CNC

Typical worm gear rotary table

Output angle

Err

orE

rror

0 90 180 270 360-0.02

-0.01

0.01

0

RollerDrive

CW

CW

CCW

CCW

Approved Performance

Performance By Zero-Backlash Technology

Be Distinctive

by Sankyo Automation

TM

The main part of the RollerDrive mechanism consists of an input shaft and an output turret in which roller followers are embedded. An integral cross-roller bearing supports the output turret with minimal run out.

Preloaded roller followers contact the input rib surfaces with a wedge-shaped cross section, which can be adjusted by moving the input axis, to eliminate backlash completely. No backlash means superior precision and stiffness for both CW and CCW rotation, as shown on the diagram to the right.

Even with preload and zero-backlash, the needle-bearing type roller followers transmit power by rolling rather than sliding making it possible for the RollerDrive to achieve an outstanding efficiency of 90% or more and life-time wear-free durability.

All parts are made from only qualified alloy steels, and machined and ground with our ultra-precision machining system.

RollerDrive product series are widely used in various industries that require the highest in performance levels. Machine tool companies are not an exception and RollerDrive technology is already being applied to the world’s leading machine tools.

The “RollerDrive QUALITY” logo encompasses rotary axis speed, precision, and mechanical stiffness - essential performance qualities for standing up to heavy cutting work. This logo is available to RollerDrive users to make their applications distinctive in their market. Contact Sankyo Automation for details on the use of this logo.

Overview

Exclusive Zero Backlash Structure

Roller followers Roller gear cam (input)

Turret(output)

Features• No backlash• Power transferred by rolling contact eliminates wear• High accuracy and good efficiency• Preloadable for high rigidity

Rolling contact Preload

Stud

Outerraceway

Roller gearcam surface

Needles

Preload Mechanism Internal Construction of the Roller Follower

• Worm gear modelsMaintenance costs occur once or twice a year to adjust thebacklash.

• RollerDriveLong-term use is possible without any mechanicalmaintenance.Beats the cost of a worm gear even after adding annualrunning costs to the initial investment cost. Priceperformance continues thereafter.

Cost Comparison Versus Worm Gear Rotary TableOffers Long-term Use Low Maintenance

$20,000

$10,000

01 2 3 4 5 6 7 Year

Cost simulations are based on a table diameter of about 200 mm.

Initial Cost versus Annual Maintenance Costs

Worm gearrotary table

Roller drive

Cost becomes less than theworm gear table in three years.

• Worm gear modelsAccuracy declines over time. Requires maintenance toachieve initial accuracy.

• The RollerDriveAccuracy is consistent with no maintenance even after 5 million operation cycles. (Requires regular oil changes)

Consistent long-term accuracy without need forbacklash adjustment.

30

20

10

00 1 Million 2 Million 3 Million 4 Million 5 Million

Operating cycles

Positioning Accuracy Aging Test

High

Low

Positioning E

rror

The RollerDrive graph is based on internal testing.

（arc sec）

Maintenance

Maintenance

Worm gear rotary t

able (example)

RollerDrive

Requiresmaintenanceat regularintervals

Drop in accuracy overtime

Consistent long-termaccuracy withoutmaintenance.

Based on internal calculations.

Low Maintenance and Excellent Price Performance

① Worm gear rotary tables require maintenance twice a year.② Assumes an annual running cost of 3% (oil changes, etc.) for both types.

Servo Motor

Preload + Rolling contact achieveszero-backlash and long life

Outstanding rotating accuracy and rigiditywith the integrated cross roller bearing

Shock resistant, high-performancecam followers

Overview

Technical Information

This indicates the percent of input power which is transmitted to the output. The motion mechanism has high efficiency because it employs rolling contact. Efficiency varies depending on conditions such as load torque, rotation speed and temperature.

In the , all rotating elements operate in a state of rolling contact, and thus there is almost no wear, or degradation in accuracy over time.

There is almost no change in positioning accuracy after testing operation (5) million times, and this shows that the outstanding accuracy of the can be maintained over the long term.

EfficiencyRCC250

Effi

cien

cy［％］

Torque［N・m］

02000 400

5 rpm

Output rotation speed

10 rpm20 rpm50 rpm

10

20

30

40

50

60

70

80

90

100

DurabilityTest of changes in RollerDrive positioning accuracy over timeRollerDrive ®

Exactness, forward direction（CCW）

Exactness, reverse direction（CW）

Repeat accuracy, forward direction（CCW）

Repeat accuracy, reverse direction（CW）

0

10

20

30

Out

put p

ositi

onin

g ac

cura

cy［ar

c. s

ec.］

Number of operations (Times)

Test Conditions

RollerDrive size

Output load weight

Output load moment of inertia

Output rotation angle

Output maximum rotation speed

Acceleration time

Constant speed time

Deceleration time

RCC250 class test machine

152 kg（φ500mm）

4.69 kg・m2

0-345 degree（Reciprocating）

100rpm

0.100 sec

0.475 sec.

0.100 sec.

RollerDrive®

0 620,000 1,320,000 1,500,000 2,000,000 2,700,000 3,000,000 4,000,000 5,000,000

RollerDrive®

RollerDrive®

Technical Information

Backlash, Lost Motion & Hysteresis Loss

General Hysteresis Graph

Rated torque

Rated torque

Lost motion

Torque acting on output

Tors

ion

angl

e

Torque acting on output [N•m]

Tors

ion

angl

e [ra

d.]

y

Backlash

Hysteresis loss

−3％ ＋3％ 50％

−0.0003−100 −50 0 50 100

0.0003

−0.0002

0.0002

−0.0001

0.0001

0.0000

Hysteresis GraphRollerDrive ®

x

Backlash Rotation angle which can arise even with zero torque (looseness)Lost motion Torsion angle of the midpoint of the hysteresis curve width which arises when applying ±3% rated torqueHysteresis loss Torsion angle where there is no complete return, when torque is applied in both forward and reverse directions

RCC250

−＋

RollerDrive ®

For a general reducer, the hysteresis graph can be obtained by applying torque to the output shaft, and plotting the generated torsion angle.

Backlash, lost motion and hysteresis loss can each be defined from the hysteresis graph, as indicated above.

Lost motion and hysteresis loss depend on the material characteristics, and occur in all types of structures. Backlash, on the other hand, occurs only when there are gaps or looseness in the structure. Backlash has a major effect on accuracy, servo gain and similar factors, and must be minimized.

With , backlash is completely eliminated using our unique preload structure, and lost motion and hysteresis loss are controlled to extremely small values due to the results of research on optimizing materials and structures.